JP4454413B2 - Stamper for forming optical recording disk substrate and optical recording disk - Google Patents

Description

  The present invention relates to an optical recording disk substrate molding stamper for molding a transparent substrate of an optical recording disk, and relates to a transparent substrate molded using the stamper and an optical recording disk including a recording layer. It is.

In recent years, optical recording disks represented by CDs and DVDs and recording / reproducing drives thereof have been widely used in the world.
These optical recording disks are used for storing data information, image information, and the like. At present, optical recording discs are being recorded at high speeds and high density recordings. On the other hand, the price of recording / reproducing drives and optical recording discs is increasing, and disk manufacturers improve the quality at low prices. There is a need to provide an optical recording disc.

In order to perform recording / reproduction with a commercially available drive, an optical recording disk needs to comply with a standard in order to ensure recording / reproduction compatibility.
As a matter of course, it is necessary to ensure the quality of the entire surface of the optical recording disk (from the inner periphery to the outer periphery).
As described above, in recent optical recording disks, high-speed recording and high-density recording make it very difficult to ensure quality over the entire surface, and it is very important.

In the production process of an optical recording disk, a basic transparent substrate is formed and then each layer is formed thereon. However, both the substrate and each layer cause differences in the production process.
In particular, when a transparent substrate is produced, the current production method (generally an injection molding method is used) always causes a difference in the shape of the recording layer forming groove formed on the transparent substrate.

 Therefore, in recent years, the stamper for forming the groove shape (convex portion) for forming the recording layer of the transparent substrate has a difference between the inside and outside of the stamper groove shape (convex shape). Various attempts have been made to compensate for the difference in the groove shape for recording layer formation.

  That is, as a conventional technique for providing a difference in the groove shape (convex shape) of the stamper, for example, the groove shape (depth and width) of the transparent substrate and the stamper is changed from the inner periphery toward the outer periphery. (For example, refer to Patent Document 1).

  Further, for example, the width of the groove shape of the transparent substrate and the stamper is increased from the inner periphery toward the outer periphery, the width of the outer land is made smaller than that of the inner periphery, and the inclination angle θ of the side surface of the groove shape on the outer periphery is set. There is a stamper that is smaller than the inner peripheral side (see, for example, Patent Document 2).

  Further, for example, there is an optical information medium in which the groove shape of the transparent substrate becomes wider or deeper from the inner periphery toward the outer periphery (having a reproduction method different from CD and DVD) (see, for example, Patent Document 3).

  For example, there is an optical storage medium in which the groove shape of the transparent substrate becomes wider or deeper from the inner periphery toward the outer periphery (see, for example, Patent Document 4).

Japanese Patent Laid-Open No. 05-198012 JP 2000-242976 A JP 2002-163842 A JP 2002-237100 A

The transparent substrate of the optical recording disk is generally formed by injection molding using a stamper. However, in the conventional examples shown in Patent Documents 1 to 4, the optical recording disk for high density and high linear velocity recording is used. Is not suitable for our study.
In particular, in the conventional example shown in Patent Document 2, the inclination θ of the side surface of the groove shape and the ratio of the inner peripheral width to the outer peripheral width of the groove are also defined. It has become clear that it is not suitable for molding optical recording disks.

In the injection molding method, it is clear from our examination results that the slope of the groove-shaped side surface for the recording layer on the outer peripheral side becomes smaller than that on the inner periphery when the transparent substrate is manufactured.
Our study results show that the slope of this side has a great influence on the recording characteristics, and it is necessary to reduce the inside / outside difference of the slope of the groove-shaped side. It becomes larger than the convex part formed in the stamper.

Certainly, in injection molding, it is difficult to form a groove shape (convex shape) on the outer peripheral side for both the transparent substrate and the stamper. However, the smaller the slope of the side surface of the groove shape (convex shape) is, the smaller the molding is on the outer peripheral side. Becomes easier.
By using this stamper, the difference in depth of the groove shape can be reduced and the uniformity of unrecorded characteristics (Push-Pull) can be improved, but the recording characteristics are deteriorated.
From our examination results, it was found that the uniformity of the groove shape depth can be secured by optimizing the molding conditions.

  The present invention relates to a stamper for forming an optical recording disk substrate, which has a good recording quality over the entire surface of the optical recording disk by providing a difference in the inclination of the groove shape (convex shape), and the optical recording disk The purpose is to provide.

The invention of claim 1, have a guide groove formed of convex portions on the transparent substrate of the optical recording disk, an optical recording disk stamper for molding a substrate for use in the injection molding method of pouring from the inner periphery of dissolved hot resin In
The stamper for forming an optical recording disk substrate is characterized in that the inclination θ of the side surface of the convex portion increases from the inner periphery toward the outer periphery.

  According to a second aspect of the present invention, there is provided a stamper for forming an optical recording disk substrate, wherein an inclination θ of a side surface of the convex portion on the inner peripheral side is 40 ° to 55 °.

  The invention according to claim 3 is the stamper for forming an optical recording disk substrate, wherein the slope θ of the side surface of the convex portion on the outer peripheral side is 45 ° to 60 °.

  According to a fourth aspect of the present invention, there is provided a stamper for forming an optical recording disk substrate, wherein the full width at half maximum of the convex portion is the same from the inner peripheral side to the outer peripheral side.

  The invention according to claim 5 is characterized in that the groove depth of the grooves between the convex portions or the height of the convex portions increases from the inner peripheral side toward the outer peripheral side. A stamper for forming a recording disk substrate.

  According to a sixth aspect of the present invention, there is provided an optical recording disk comprising an organic dye formed on the optical recording disk substrate formed by the stamper according to any one of the first to fifth aspects. It is a recording disc.

  According to the present invention, a stamper for forming an optical recording disk substrate that can have good recording quality over the entire surface of the optical recording disk by providing a difference in the inclination of the groove shape (convex shape), and optical A recording disk can be provided.

In particular, according to the first aspect of the present invention, uniform signal quality can be obtained over the entire surface.
According to the second aspect of the present invention, it is possible to obtain a good signal quality on the inner periphery.
According to the third aspect of the present invention, it is possible to obtain a good signal quality at the outer periphery.
According to the fourth aspect of the present invention, it is possible to obtain a disc having a small recording sensitivity inside / outside difference.
According to the fifth aspect of the present invention, it is possible to obtain a disc with good unrecorded (Push-Pull) uniformity.
The invention according to claim 6 can exhibit the effect of this patent most.

  Hereinafter, an optical recording disk molding stamper and an optical recording disk according to an embodiment of the present invention will be described. First, prior to the description of the present embodiment, a general method for manufacturing an optical recording disk will be described. To do.

An optical recording disk is generally formed by the following method. First, a stamper in which a guide groove (convex portion) for forming a recording layer on a transparent substrate is formed on a molding die attached to a molding machine.
For example, a polycarbonate resin dissolved at a high temperature is poured into a molding die, and the stamper guide groove (convex portion) is transferred by applying pressure and pressing the stamper while controlling the temperature of the die. Mold the disc.

However, since it is an injection molding method in which a high-temperature resin melted from the inner periphery is poured, a temperature gradient is created in the mold, so that the guide groove for molding the recording layer of the completed molded substrate (transparent substrate) An internal / external difference occurs in dimension.
When there is no difference between the inside and outside of the stamper guide groove (groove shape or convex shape), the guide groove (groove shape for forming the recording layer) of the molded substrate (transparent substrate) is deep on the inner peripheral side and has a large inclination θ and the outer periphery. It is known by AFM measurement (Atomic Force Microscope: using an evaluation machine made by Digital Instrument) that the inclination θ is shallow at the side.
That is, the inner peripheral side of the transparent substrate has almost completely transferred the groove shape (convex portion) of the stamper, but the outer peripheral side does not enter the depth of the groove shape (convex shape) of the stamper. It is clear that the transfer becomes incomplete and the inclination θ is also reduced. However, the half width of the groove shape on the outer peripheral side is substantially the same as that on the inner peripheral side.

On the other hand, a recording layer, a reflective layer, and a protective layer are sequentially formed on the transparent substrate to complete an optical recording disk.
However, an intermediate layer is laminated between the layers by the optical recording disk, and an adhesive layer and a cover substrate are laminated on the protective layer.

Since the optical recording disk is recorded by a commercially available recording drive, information is carved by the meandering of the groove in the above-mentioned guide groove (groove shape for forming the recording layer). Information that can be read by the reproduction drive is recorded in the reading and guiding grooves.
Therefore, the information carved in the guide groove (groove shape) is a very important characteristic. In particular, in the case of an optical recording disk for high-speed recording and high density, ensuring the quality is as important as the recording characteristic. .

The meandering signal of the guide groove (groove shape for forming the recording layer) is called a wobble signal, and its SN ratio needs to be secured to a certain level.
Since the SN ratio of the wobble signal is greatly influenced by the groove shape of the molded substrate (transparent substrate), a groove shape that can ensure this SN ratio is required.
In the case of a high-density optical recording disk, since it is influenced by the adjacent guide groove (groove shape), the SN ratio of the wobble signal is improved by narrowing the groove width or increasing the inclination of the side surface of the groove. .

On the other hand, as the groove shape of the transparent substrate that affects the recording characteristics, it has been found from our examination results that the characteristics are improved by increasing the groove width and reducing the inclination of the side surface of the groove.
As the groove shape of the transparent substrate that affects the recording sensitivity (recording power that can obtain the optimum recording characteristics), the groove width (half-value width), the groove depth is deep, and the recording sensitivity increases when it becomes shallow (required recording power) ). For this reason, the recording sensitivity needs to reduce the internal / external difference.

In consideration of the groove shape and signal characteristics of the molded substrate (transparent substrate) described above, the groove shape (convex portion) of the stamper is formed so that the inclination of the side surface of the groove shape of the molded substrate (transparent substrate) is the same. By doing so, it is possible to obtain an optical recording disk having good characteristics with no difference between inside and outside.
However, if the stamper is provided with a groove shape (convex shape) width difference (thinning the outer periphery), the recording sensitivity difference is deteriorated.
Further, when the groove shape width and the side surface inclination are changed with respect to the entire surface of the transparent substrate, either the SN ratio of the wobble signal or the recording characteristics deteriorates.

  Table 1 below shows signal characteristics when the width (half-value width) of the groove shape (convex shape) of the stamper and the inclination of the side surface of the groove shape (convex shape) are changed on the inner peripheral side (radius 25 mm to 28 mm).

  Table 1 shows the measurement results when a DVD write-once disc DVD + R is used as the optical recording disc. For recording and wobble measurement, DDU-1000 (NA: 0.65, manufactured by Pultec) is used. Wavelength: 657 nm) was used, and DDU-1000 (NA: 0.60, wavelength: 650 nm) was used for reproduction. Recording was performed at 6 × speed recording (20.9 m / s 2).

  From Table 1, it can be seen that the groove width of Sample-4 is 0.32 nm and the inclination angle is 49 °, the wobble SN ratio and DC jitter are both high, and the recording sensitivity mW is also the highest. The groove width of Sample-5 is 0.48 nm and the inclination angle. When the angle is 49 °, both the wobble SN ratio and DC jitter are low, and the recording sensitivity mW is also the lowest.

  Table 2 below shows the results of measuring the groove shape of a molded substrate (transparent substrate) molded with a stamper having no difference in inside and outside of the groove at half maximum width, groove inclination, and groove depth.

From Table 2, when the groove shape is formed on the molded substrate (transparent substrate) using the groove half width of 0.37 nm and the side surface tilt angle of 49 ° according to the preset stamper, the groove slope on the inner peripheral side is also 49 °. And the groove depth was 0.158 nm.
However, it was found that the groove inclination on the outer peripheral side of the molded substrate (transparent substrate) narrowed to 45 ° and the groove depth also decreased (shallow) to 0.153.
As a result, the stamper is formed by setting the slope θ of the side surface of the convex shape (groove shape) that forms the guide groove (groove shape for forming the recording layer) on the transparent substrate to be increased from the inner periphery toward the outer periphery. It can be seen that it is possible to eliminate the difference in inclination of the side surface of the guide groove (groove shape) of the substrate (transparent substrate).

  In the stamper, the side surface of the convex shape (groove shape) that forms the guide groove (groove shape for forming the recording layer) on the transparent substrate is set to be larger from the inner periphery toward the outer periphery. The optical recording disc can obtain good signal characteristics on the entire surface.

Moreover, when the slope θ of the side surface of the convex shape (groove shape) on the inner peripheral side of the stamper is 40 ° to 55 °, good wobble characteristics and recording characteristics can be ensured.
Further, since the inclination of the groove-shaped side surface on the outer peripheral side of the molded substrate (transparent substrate) tends to drop by about 5 ° compared to the inner periphery, the inclination of the groove-shaped side surface on the outer peripheral side is 45 ° to 60 °. There must be.

  It has been found that there is no difference in the half width of the groove shape of the molded substrate (transparent substrate) molded by the stamper, and the convex shape (groove shape) of the stamper is also used to reduce the difference in recording sensitivity. It is preferable that the groove half-widths are all the same and that there is no difference between the inside and outside.

  Since the groove depth of the groove shape on the outer peripheral side of the molded substrate (transparent substrate) tends to be shallower than that on the inner peripheral side, the groove depth of the convex shape (groove shape) on the outer peripheral side of the stamper is on the inner peripheral side. By making the depth deeper, it is possible to improve the unrecorded uniformity. Desirably, it is desirable to deepen the outer peripheral side by about 50A.

In the case of an organic dye-based optical recording disk, recording not only alters the recording layer but also deforms the molded substrate (transparent substrate) to form a recording mark, which is easily affected by the molded substrate (transparent substrate). .
Therefore, in the case of an optical recording disk having an organic dye-based recording layer, it is possible to obtain the greatest effect by molding it with a molding substrate (transparent substrate) that has been optimized as described above.

  Next, a stamper for forming an optical recording disk according to the present embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view for explaining the configuration of a stamper according to the present embodiment. The left side in the figure shows a part on the inner peripheral side, and the right side in the figure shows a part on the outer peripheral side.

As shown in FIG. 1, the stamper 11 of the present embodiment has, for example, a convex portion 13 for forming a groove shape for forming a recording layer of a transparent substrate formed on one surface.
The slope θ of the side surface 15 of the convex portion 13 is formed so as to gradually increase from the inner periphery to the outer periphery corresponding to one surface of the optical recording disk.

  The inclination θ of the side surface 15 on the inner peripheral side of the convex portion 13 of the stamper 11 is, for example, 40 ° to 55 °, and the inclination θ of the side surface 15 on the outer peripheral side (13 ′) of the convex portion 13 is 45 ° to 60 °. It is.

The full width at half maximum W3 (W3 ′) of the convex portion 13 of the stamper 11 is the same size from the inner peripheral side to the outer peripheral side.
That is, when the width of the land 17 of the convex portion 13 on the inner peripheral side is W1 and the width of the foot 19 of the convex portion 13 is W2, W3 = (W1 + W2) / 2 is established.
W3 ′ = (W1 ′ + W2 ′) / 2 is also established when the width of the land 17 of the convex portion 13 ′ on the outer peripheral side is W1 ′ and the width of the foot 19 of the convex portion 13 ′ is W2 ′. .
And W3 = W3 ′, which is the same over the entire circumference.

  Further, the groove depth between adjacent convex portions 13 (13 ′) of the stamper 11 or the height d (d ′: d <d ′) of the convex portion 13 (13 ′) is the inner circumference side. It is set so that it may become large toward the outer peripheral side.

  When the groove-shaped groove depth between adjacent convex portions 13 (13 ′) of the stamper 11 or the height d of the convex portion 13 (13 ′) increases from the inner peripheral side toward the outer peripheral side, Since the full width at half maximum W3 (W3 ′) of each convex portion 13 is the same over the entire circumference, the width W4 of each groove-shaped groove 21 tends to increase from the inner peripheral side toward the outer peripheral side. The dimension of the width W4 of each groove 21 may be set to be the same over the entire circumference, that is, may be set arbitrarily.

Even when an optical recording disk is formed using the stamper 11 of the present embodiment, first, a guide groove (convex portion 13) for forming a recording layer on a transparent substrate is formed in a molding die attached to a molding machine. The stamper 11 is attached.
For example, a polycarbonate resin dissolved at a high temperature is poured into the molding die, and pressure is applied and the stamper 11 is pressed while controlling the temperature of the die, whereby the convex portion 13 (groove shape) of the stamper 11 is transferred. A disk of a transparent substrate (see FIG. 2) 31 is formed.

As shown in FIG. 2, the transparent substrate 31 formed by the stamper 11 has a groove 33 for forming a recording layer formed on one surface thereof.
The half width of the groove shape 33 of the transparent substrate 31 is uniformly the same width W3 from the inner peripheral side to the outer peripheral side, and the groove shape depth d is also uniformly the same depth toward the outer peripheral side. It is in.

  A recording layer 35 is formed on the transparent substrate 31, a reflective layer 37 is formed on the recording layer 35, and a protective film 39 is formed on the reflective layer 37, thereby forming an optical recording disk 41. The

As an example of the present embodiment, the above-mentioned stamper 11 was used to mold a DVD write-once disc DVD + R as the optical recording disc 41, and the effect of the groove shape 33 was confirmed.
For recording and wobble measurement (unrecorded), DDU-1000 (NA: 0.65, wavelength: 657 nm) manufactured by Pultec was used, and for reproduction, DDU-1000 (NA: 0.60, wavelength: 650 nm). Recording was performed at 6 × speed recording (20.9 m / s 2).
On the other hand, the convex portion (or groove shape) 13 of the stamper 11 is measured by an AFM constant apparatus manufactured by Digital Instrumental.

  Table 3 below shows the measurement results of the groove shape 33 for the recording layer molded on the transparent substrate 31 of the DVD write-once disc DVD + R using the stamper 11, and the upper stage is the inner circumference and the lower stage is the outer circumference measurement. It is a result.

  As shown in Table 3, compared to the case where a transparent substrate was molded with a conventional stamper (Comparative Example-1), Examples-1 and 2 were able to improve the internal and external differences in jitter and wobble SN characteristics. In Example-3, it became clear that Push-Pull uniformity could be improved.

In the present embodiment, the inclination θ of the side surface 15 on the inner peripheral side is, for example, 40 ° to 55 °, the inclination θ of the side surface 15 on the outer peripheral side is 45 ° to 60 °, and the full width at half maximum extends over all sides. Since the stamper 11 is formed by forming the convex portion 13 which is the same and the groove depth or height of the groove increases toward the outer peripheral side, it is possible to have good recording quality over the entire surface of the optical recording disk 41. It became.
In addition, the optical recording disk 41 of the present embodiment formed by the stamper 11 was able to improve the internal and external differences in jitter and wobble SN characteristics, and improve the push-pull uniformity.

  The recording layer 35 of the transparent substrate 31 formed by the stamper 11 is preferably an organic dye, and when the organic dye is used, the above-described effects can be exhibited most.

It is a partial sectional view explaining the composition of the stamper concerning an embodiment of the invention. It is sectional drawing explaining the structure of the optical recording disk containing the transparent substrate shape | molded with the said stamper.

Explanation of symbols

11 Stamper 13 Convex part 15 Side surface 17 Land 21 Groove 31 Transparent substrate 33 Groove shape 35 Recording layer 41 Optical recording disk

Claims (6)

Have a guide groove formed of convex portions on the transparent substrate of the optical recording disc, the stamper for optical recording disk substrates molded using an injection molding method of pouring from the inner periphery of dissolved hot resin,
A stamper for forming an optical recording disk substrate, wherein the slope θ of the side surface of the convex portion increases from the inner periphery toward the outer periphery.   2. The stamper for forming an optical recording disk substrate according to claim 1, wherein an inclination θ of a side surface of the convex portion on the inner peripheral side is 40 ° to 55 °.   The stamper for forming an optical recording disk substrate according to claim 1 or 2, wherein an inclination θ of a side surface of the convex portion on the outer peripheral side is 45 ° to 60 °.   4. The stamper for forming an optical recording disk substrate according to claim 1, wherein a half width of the convex portion is the same size from the inner peripheral side to the outer peripheral side. 5.   The groove depth of the groove between the convex portions or the height of the convex portion increases from the inner peripheral side toward the outer peripheral side. A stamper for forming an optical recording disk substrate according to 1.   6. An optical recording disk, wherein a recording layer made of an organic dye is formed on an optical recording disk substrate formed by the stamper according to any one of claims 1 to 5.

Images